The lack of scientific attention devoted to the placebo effect as a phenomenon in its own right probably reflects the paucity of theoretical positions within which to organize the existing data and design new research. The proposed investigation 1) is an attempt to advance from a descriptive to an experimental analysis of the placebo effect, taking into account classical conditioning effects, and 2) examines the clinical implications of partial reinforcement as it is applied to the treatment of insomnia. Subjects with primary insomnia will be treated with zolpidem for a period of one month and then randomized to one of four groups for a period of 12 weeks: one receiving full dose zolpidem on a nightly basis (continuous reinforcement), one receiving full dose zolpidem on 14 of 28 nights where placebo is provided on non-drug nights (partial reinforcement), one receiving full dose zolpidem on 14 of 28 nights where no pills are imbibed on non-drug nights (intermittent dosing), and one receiving 5 mg dose zolpidem on a nightly basis (continuous reinforcement with half the standard dose). Following treatment, subjects will be entered into an extinction protocol during which they will 1) continue on the schedule assigned during the experimental period, 2) receive only placebo, or 3) receive neither drug nor placebo. Sleep and daily functioning will be monitored on a daily basis via sleep diaries for the duration of the study. It is hypothesized that, holding cumulative dose constant, a partial schedule of reinforcement will enable patients to better maintain their clinical gains as compared to subjects that receive either continuous reinforcement with half the standard dose or half the frequency of use. Relevance: The proposed research is not an attempt to offer a behavioral alternative to drug treatment;it is an attempt to acknowledge and capitalize on a behavioral dimension in the design of drug treatment protocols. The value of the proposed research resides in its capacity to provide for the long term treatment of insomnia in a manner that increases the durability of pharmacotherapy while reducing the overall amount of medication required. If proven effective in the current application, this new approach to pharmacotherapy and placebo effects is likely to stimulate new interdisciplinary research for the treatment of a variety of chronic diseases.